All full size a/c will climb with power, and descend without power. Your Pilatus will fly level at one power setting. That is governed by the angular set up between the wing and tailplane, and the weight of the model. So far there is not much you can do about that, you can play around with downthrust, but the real one doesn't have strange thrust angles, the pilot just uses power to climb, trim to fly straight, at some lower power 'cruise' setting, and descends at idle. Perhaps, instead of trying to fly it like an aerobatic 'pattern' airplane, which is a pretty artificially designed 'one task' model, you should fly it like the real thing. Take an 'intoductory' at you local full size field, and see how the pilots juggle trim, power and airspeed, then try it with the Pilatus, much more satisfying to fly it properly, than just 'driving' it around the sky.
Evan, WB #12.